If you want to operate a hardware fax on a VoIP connection, you must either connect it directly to the Fritz!Box or use an adapter like the Cisco SPA112.
The operation of a analog fax machine is not necessarily easy for customers with an "All-IP" connection (or whatever the respective provider calls the product). Analogue devices can be connected to the Fritz!Box, but sometimes the space for the fax machine (if it is a multifunction printer as in my case) is far away from the Fritz!Box, in my case it would be impossible or at least very unattractive to lay a corresponding cable across the flat. The solution: a Cisco SPA112 adapterthat accesses the Fritz!Box as a SIP proxy.
The advantage Fax machine (in my case an HP All-in-One OfficeJet 5610) can be left in the study, the Fritz!Box near the telephone connection. For occasional faxing the variant over Roger routeronly if you're more often Sending faxes via the VoIP connection will, one should consider this alternative. The trick: because the Fritz!Box acts as a proxy, you don't need to make any difficult and complicated settings to integrate the SPA112 directly as a device at the Telekom.
The CISCO SPA112 is a VoIP adapterswhich enables the connection of two telephones or fax machines. Actually, the configuration is quite complicated, but in cooperation with a Fritz!Box, which acts as a SIP proxy, this can be simplified considerably: setting up as a separate device with the telecom access data is not necessary.
Preparing the Fritz!Box 7490 for Cisco SPA112
A VoIP telephone must be installed in the Fritz!Box. This is done via "Telephony" -> "Telephony equipment"There a password is set and a user name is displayed when a new password is created.
Once the new telephony device has been created in the Fritz! box, you can start configuring the SPA112.
Configuration Cisco SPA112
The Cisco SPA112 offers a very extensive configuration. Fortunately, this setup only requires the "Quick" configuration, so you don't have to bother with the details. Basically, you only have to enter the data from the Fritz!Box configuration:
If everything went well, you can see under "Voice" -> "Information" the status "Registered" for the port configured in each case. If everything works, you can both send and receive faxes with the connected device - both via the existing VoIP connection without additional services like Sipgate. The only disadvantage: Telekom supports the standard T.38 not, so that the fax transmission is a little more error-prone.
The configuration under "Voice" -> "Line 2" -> "Audio" looks like this in my setup, T.38 is explicitly disabled:
The Cisco adapter is available for about 40,- Euro used in Amazon Marketplace
Fax storage & forwarding
In the configuration of the Fritzbox you can choose whether to store incoming faxes on the internal memory, save them on a connected USB stick or forward them by mail.
For forwarding by mail to work, an e-mail server must be configured for sending under System -> PUSH-Service -> Sender.
If you are surprised that sending faxes does not work with current Fritz!OS versions: AVM has increased the demands on VoIP phones (including the SPA112 box). Both password and user name must now be eight characters so that the box can log on to the Fritzbox. If you have adjusted this accordingly, it works again without any problems.
Update July 5, 2019:
In the meantime I have changed the setup so that the FritzBox can receive faxes itself. So the actual fax machine doesn't have to stay switched on if you don't want to send anything. Therefore simply activate the fax function with the same number in addition to the VoIP device configured above: